Flat actuators, formed from layers of piezoelectric fibers parallel to one direction and sandwiched between layers carrying electrodes oriented perpendicularly to these fibers in order to activate them, have already been developed in order to slide two structure elements with respect to each other. The applications sought in aeronautics are for example the controlled deformation of an aerodynamic element in order to adapt it according to its variations in incidence.
In this type of application, the performance of the actuator in the shear direction is expressed by the value of the corresponding angular distortion.
The applicant has already proposed, in the document FR 2 893 783, a rectangular flat actuator producing a shear in the direction of its long edge, consisting of an active layer of piezoelectric fibers sandwiched between two layers carrying parallel electrodes, themselves each covered with a layer of fabric with rigid warp and weft oriented in two directions forming a mesh. The weft and warp define a mesh of juxtaposed deformable parallelograms. The piezoelectric fibers form an angle of 45° with the long edge and 90° with the electrodes. The various layers are adhesively bonded to each other so as best to transmit the shear movement of the planar layer of piezoelectric fibers. The layers of fabric with rigid warp and weft provide both the transmission of the shear movement to the members on which the actuator is installed and the rigidity of the device in the other directions.
The drawback of this device is the limited amplitude of the angular distortion allowed by an elementary module of this type of actuator. Whatever the piezoelectric material used in the fibers, the tests carried out by the applicant result in a mean angular distortion of 1256 μclef at 45° for a fiber deformation of 800 μdef.